Here’s a new beta version of my tool pngdump.py, a tool to analyze PNG files.

I took a look at all files on MalwareBazaar with a PNG tag, and made updates to pngdump.py to handle them.

I found 3 types of “PNG” files.

First, files spoofing PNG files: files that are not PNG files, but have a .png extension.

Like .exe and .rar files:

Second, valid PNG files with an appended payload:

Third, invalid PNG files. For example, PNG files with the right record structure, but where the Zlib compressed image is replaced by an RC4 encrypted payload (IcedID):

I also have other samples, but that’s for another blog post.

Beta version 0.0.3 is available on GitHub.